Efficient sharing of a resource in a radio access network (e.g. time-slots in GSM/EDGE, codes and power in WCDMA) can be obtained by a scheduling function that assigns and reassigns resources among a multitude of connections. Important examples of such scheduling functions are the schedulers used in radio base stations with High Speed Downlink Packet Access (HSDPA).
Access to a shared channel such as High Speed Downlink Shared Channel (HS-DSCH) in HSDPA is handled in the radio base station by the scheduling function. At each scheduling instant, resources necessary to transmit data over the shared channel are temporarily assigned to one or a few users. The scheduling decision, i.e. which users to select, at each instant is typically based on current user specific information such as delay (since last transmission) and radio link quality. A well-known method is proportional fair (PF) scheduling that achieves good performance by utilizing temporal link quality variations (multi-user diversity) while maintaining fairness in the sense of round robin (RR) scheduling.
In scenarios where file transfer, i.e. file download or file upload, is a common user service, there may be users with very large downloads. These users will need resources for a relatively long time, in particular if they in addition have a radio link with low bit-rate. For standard scheduling methods, such users might have significant impact on the performance experienced by other users. Thus, it is desirable to identify such users and take their specific demands into account when making the scheduling decisions.
Previously known scheduling methods designed to handle large files, such as the foreground-background (FB) scheduler and the shortest remaining processing time (SRPT), take the number of bits into account. However, these methods imply the problem that they do not utilize multi-user diversity and are therefore less suitable for a radio channel.